A hot air oven was previously used for heat treatment of a mixture of cellulose fibers and thermoplastic fibers to melt the thermoplastic fibers and produce a binding action. The thermoplastic fibers must be heated to their melting point during a certain time period in order for satisfactory binding to take place. Such a thru-air heater is disclosed in, e.g., Swedish Patent Specification No. 199,787.
An alternative method for achieving the necessary heating is the use of heated rollers.
The use of infrared radiation for activating nonwoven cellulosic materials has indeed been suggested previously, but no practical method or apparatus has been designed for this purpose except the method and apparatus described in the above-mentioned U.S. patent application No. 073,525, now abandoned. However, certain improvements to this method and apparatus are needed to more effectively control the path of the air flow and the amount of air passing through the nonwoven material.
The present invention relates to a new method and a new apparatus that are specifically suitable for using the principles described in U.S. patent application No. 073,525, now abandoned.
Many napkin machines include a so-called "tissue portion". According to the present invention, the tissue material in the napkin is unnecessary and that entire portion of the machine can be replaced by the present invention. In this case, the length of the complete napkin machine is not increased. It is always an object to decrease the web length in such machines, since as a rule, the material in the machine must be discarded when the machine is stopped. The shorter the machine, the less discarded material there will be.